This invention relates generally to releasably attachable accessory devices for use in enhancing the operation of electronic apparatus and more particularly to accessory control devices that operate upon being added to various kinds of electronic apparatus and, upon installation of the accessory control device in such electronic apparatus, enhancing information handling, processing and executing of functions in such electronic apparatus. More specifically, this invention relates to information processing devices having a configuration wherein a data bus in a first processor in the electronic apprartus transfers data from the electronic apparatus to an accessory control device installed in an inlet connector adapted for read only data capbility and methods of efficiently handling and processing information of both the information processing means of the elecronic apparatus and of the installed accessory control device.
In recent years, personal computers, word processors, workstations and other electronic apparatus operating under digital logic control, and printers, facsimile machines, electronic pocketbooks, electronic musical instruments, electronic cooking appliances, electronic cameras and other electronic apparatus operating under microprocessor control are being employed in all areas of society. Further, the use of microprocessors is spreading rapidly to applications, such as, in automobiles, robotics and machine controlled tools, as well as all other types of electric products. Such apparatus utilizing digital logic operation and software have the potential of flexible data processing as compared with simple feedback control realized only with hardware, and, further, have the advantage of being able to change essential functions or change to different functions or to upgrade existing functions through changes to their software. Therefore, it is possible to accomplish completely different control utilizing the same hardware by, for example, merely changing the contents of the ROM utilized in conjunction with the microprocessor wherein procedures are stored or loading of a new program to the main memory from an external device, such as, a floppy disk is readily accomplished. As used herein, "procedures" is meant to be interchangeable with programs, instruction set, processing, process, instructions, program control, commands and the like.
However, since the throughput of the processor that actually performs control is dependent on the hardware, e.g., a predetermined number of operations per unit time, the number of bits that can be handled at one time and width of the bus that performs data transfer, improvement by upgrading the software is limited to only improved usage. As a result, any significant improvement in the performance of the existing electronic apparatus cannot, therefore, be realistically accomplished since it is limited by the existing hardware of the electronic apparatus. Further, upgrading by changing the software requires replacement of the ROM if the software is fused into the ROM, thus making it difficult to achieve in many cases. Therefore, upgrading the software is difficult in most cases except those in which ROM replacement is designed into the device from the beginning or the software is supplied on a replaceable medium, such as, by means of a floppy disk.
In personal computers, for example, accelerators on accelerator boards mounted in the computer housing are employed to improve the functionality of the computer system by completely replacing the microprocessor. However, this requires replacement of the CPU on the motherboard or other difficult operations that cannot generally be performed by ordinary computer users. In electronic apparatus intended for use as a personal computer, an input connector is often provided for the installation of ROM cards, font cartridges and other types of cartridges. An examination of the data transfer bus of the input connectors shows that many of them are only provided with read-only capability as viewed from the electronic apparatus. In such circumstances, a processing accelerator cannot be installed in the input connector since there are no means provided for the output of data from the electronic apparatus to a device or cartrdige installed in the input connector. If an accessory control device could be installed in the input connector that us capable of also receiving data from the electronic apparatus, the functionality of the electronic apparatus could be readily improved, enhanced, added to or changed. However, this is not possible since there is no data bus capability already provided for sending data from the electronic apparatus to the accessory control device installed in the apparatus input connector.
Generally, in the past, no consideration has been made regarding the improvement or changing of the functionality of existing printers, facsimile machines, electronic pocketbooks, electronic musical instruments, electronic cooking appliances, electronic cameras and other consumer electronic apparatus containing a microprocessor, and, further, existing electrical equipment for automobiles, robots, machine tools and other industrial electronic apparatus as well as all types of electric appliances. In case of such appliances, even if expanded functionality is provided through an external input connector, it is generally restricted to functionality of read only data from a device installed in the input conenctor. This lack of consideration is now described in conjunction with respect to one particular electronic apparatus, to wit, a page printer, although it should be realized that its is not limited to this particular kind of electronic apparatus.
In recent years, the rapid development and distribution of laser printers and other page printers has become widespread with high speed output in the transfer of data from computers to such printers for printing. In the case of laser printers, their resolutions range from 240 to 800 dots per inch (DPI), and these printers are capable of printing several pages a minute. One class of these printers generally employ a xerographic unit that employs a photosensitive medium, e.g., a xerographic drum, as the print engine. Since such a print engine continuously performs each of the functions of medium charging, exposure, toner application and image transfer processes in sync with the rotation of the photosensitive drum, the printing processing immediately begins after a image for a first single page has been processed and is stored in the printer memory. As a result, the memory provided in page printers for image processing must have the capacity to hold an image for at least one page. If compression of image data is not performed, the capacity is determined by the resolution and the size of the paper that is capable of being processed. For example, in the case of a resolution of 300 DPI and a paper size of 8 inches by 10 inches, 7,200,000 (8.times.10.times.300.times.300) dots must be manipulated and at least a 0.9 megabyte memory is required to hold this page of data.
In printers that function to receive character codes, row and column pitch and other information as print data and expand this data into an image, or in printers that receive a program described by a page description language and then expand the image by interpretation of the page description, it is necessary to calculate and produce a bit image based on such print data, which greatly reduces the overall processing speed compared to simple bit image transfer since there is huge volume of information to be expanded or interpreted. In other words, the processing speed of a printer is determined principally by the throughput of the printer processor that performs processing and memory access time and it is well known that their processing capability falls far short of the printing throughput and capability of the xerographic unit itself. For example, in a page printer capable of printing 10 pages per minute, only six seconds is allowed to prepare the image data for one page (0.9 megabytes of data) of printing. To process all 0.9 megabytes of data in this period of time means that the processing time allowed for one byte is a mere 6.6 microseconds (6 s/0.9 MB). This processing speed can possibly be realized with one of the high speed RISC type processors currently available on the market today. In contrast to this, however, there are currently many xerography units in use today capable of printing 10 pages per minute. Therefore, the throughput of the controllers that process print data in these printers is a bottleneck in improving overall print speeds of presently developed printers as well as existing printers being employed by end users.
For this reason, there are situations wherein the image processing throughput is remains below the throughput capability of the xerography unit utilized in laser printers. Furthermore, even if it becomes possible to obtain a processor with a high image processing throughput as the microprocessor technology continually advances, it is impossible to improve image processing functionality later in these printers already in the hands of end users.
There are some page printers whose functionality can be improved by being able to increase internal memory capacity or by providing an expansion slot and installing a cartridge with built-in fonts or programs stored in the cartridge but the structure of the data bus of the slot connector is designed for read only capability from the cartridge connector so that data cannot be transferred from the electronic apparatus to the cartridge and processed in the cartridge in conjunction with a separate cartridge processor and programs provided in the cartridge adapted for proper processing of the transferred data.
It is an object of this invention to provide an accessory control device for an electronic apparatus that is capable of enhancing the operation of the processor of the electronic apparatus.
It is another object of this invention is an information processing device in conjunction with an electronic apparatus for use with an accessory control device to provide for overall improvement, change in or added functionality of the electronic apparatus.